Mycelium

About: Mycelium is a research topic. Over the lifetime, 8923 publications have been published within this topic receiving 170993 citations.

Regulation of Peroxidase Transcript Levels in Liquid Cultures of the Ligninolytic Fungus Pleurotus eryngii

Abstract: A versatile peroxidase able to oxidize Mn2+ as well as phenolic and nonphenolic aromatic compounds is produced in peptone-containing liquid cultures of Pleurotus eryngii encoded by the gene mnpl. The regulation of its transcript levels was investigated by Northern blotting of total RNA. High-peroxidase transcripts and activity were found in cultures grown in glucose-peptone medium, whereas only basal levels were detected in glucose-ammonium medium. The addition of more than 25 μM Mn2+ to the former medium did not result in detectable peroxidase transcripts or activity. Potential regulators were also added to isolated mycelium. In this way, it was shown that high transcript levels (in peroxidase-expressing mycelium) were maintained on peptone, whereas expression was not induced in short-term incubation experiments. Similar results were obtained with Mn2+ ions. Strong induction of mnpl expression was caused by exogenous H2O2 or by continuous H2O2 generation during redox cycling of menadione. By the use of the latter system in the presence of Fe3+, which catalyzes the reduction of H2O2 to hydroxyl radical, it was shown for the first time that the presence of this strong oxidant causes a rapid increase of the transcripts of a ligninolytic peroxidase. In conclusion, peptone and Mn2+ affect the levels of transcripts of this versatile peroxidase in culture, and reduced oxygen species induce short-term expression in isolated mycelium, probably via a stress response mechanism.

Contribution of aerial hyphae of Aspergillus oryzae to respiration in a model solid-state fermentation system.

Abstract: Oxygen transfer is for two reasons a major concern in scale-up and process control in industrial application of aerobic fungal solid-state fermentation (SSF): 1) heat production is proportional to oxygen uptake and it is well known that heat removal is one of the main problems in scaled-up fermenters, and 2) oxygen supply to the mycelium on the surface of or inside the substrate particles may be hampered by diffusion limitation. This article gives the first experimental evidence that aerial hyphae are important for fungal respiration in SSF. In cultures of A. oryzae on a wheat-flour model substrate, aerial hyphae contributed up to 75% of the oxygen uptake rate by the fungus. This is due to the fact that A. oryzae forms very abundant aerial mycelium and diffusion of oxygen in the gas-filled pores of the aerial hyphae layer is rapid. It means that diffusion limitation in the densely packed mycelium layer that is formed closer to the substrate surface and that has liquid-filled pores is much less important for A. oryzae than was previously reported for R. oligosporus and C. minitans. It also means that the overall oxygen uptake rate for A. oryzae is much higher than the oxygen uptake rate that can be predicted in the densely packed mycelium layer for R. oligosporus and C. minitans. This would imply that cooling problems become more pronounced. Therefore, it is very important to clarify the physiological role of aerial hyphae in SSF.

Bikaverin, an antibiotic from Gibberella fujikuroi, effective against Leishmania brasiliensis.

Abstract: The red quinone C20H14O8 (mp 322–324), named bikaverin was isolated from mycelium ofGibberella fujikuroi. Bikaverin is specifically effective againstLeishmania brasiliensis while is not effective against other protozoa, bacteria and fungi. For production of bikaverin in a submerged culture the most convenient media are those with a natural source of nitrogen (corn-steep liquor, soyabean meal) in which the content of bikaverin ranged from 1.0 to 1.7% of dry weight of mycelium.

Streptomyces scabies 87-22 Possesses a Functional Tomatinase

Abstract: The actinomycete Streptomyces scabies 87-22 is the causal agent of common scab, an economically important disease of potato and taproot crops. Sequencing of the S. scabies 87-22 genome revealed the presence of a gene with high homology to the gene encoding the alpha-tomatine-detoxifying enzyme tomatinase found in fungal tomato pathogens. The tomA gene from S. scabies 87-22 was cotranscribed with a putative family 1 glycosyl hydrolase gene, and purified TomA protein was active only on alpha-tomatine and not potato glycoalkaloids or xylans. Tomatinase-null mutants were more sensitive to alpha-tomatine than the wild-type strain in a disk diffusion assay. Interestingly, tomatine affected only aerial mycelium and not vegetative mycelium, suggesting that the target(s) of alpha-tomatine is not present during vegetative growth. Severities of disease for tomato seedlings affected by S. scabies 87-22 wild-type and DeltatomA1 strains were indistinguishable, suggesting that tomatinase is not important in pathogenicity on tomato plants. However, conservation of tomA on a pathogenicity island in S. acidiscabies and S. turgidiscabies suggests a role in plant-microbe interaction.